[FEATURE] Separate type for customFields

[krzysztofkaszanek]

Description

api-gen package generates the following type for all customFields:

customFields?: GenericRecord;

where

type GenericRecord =
  | never
  | null
  | string
  | string[]
  | number
  | {
      [key: string]: GenericRecord;
    };

This caused issues for us as soon as we enabled typechecking in the project:
product.customFields['custom_product_short_description']

It seems that GenericRecord type is too generic for customFields. customFields will never be a string or number directly.

What we plan to use for now as a workaround is the following type:

type GenericRecordValue =
    | never
    | null
    | string
    | string[]
    | number
    | {
          [key: string]: GenericRecord
      }
type GenericRecord = {
    [key: string]: GenericRecordValue
}

It's far from ideal as we need to edit the auto-generated storeApiTypes.d.ts manually.

I think the best solution would be to introduce new, more specific type for customFields field.

Use Case

Introducing new type specifically for customFields will resolve the type errors when trying to access custom field value.

Proposed Solution

Introduce separate, more specific type for customFields

Alternatives Considered

No response

Additional Context

No response